Modern passenger vehicles, such as cars, buses and trucks, are to an increasing degree provided with equipment and assist systems for partly or fully automating one or more driving functions of the vehicle, such as steering, lane keeping, parking, speed control, etc.
A vehicle may be provided with any degree of automation of its driving functions, ranging from a fully developed autonomous drive system or AD system to an assist system where only one or a few functions are automated. A fully developed AD system makes the vehicle capable of being safely steered and maneuvered through traffic without the need for a human driver using driving equipment such as a steering wheel or pedals while the vehicle is driven in the AD mode. Less developed automated systems may assist a driver in performing one or more actions such as steering the vehicle, parking the vehicle, keeping a safe distance to a preceding vehicle, staying within a lane, etc.
Switching between a manual driving mode and an automated/assisted driving mode is generally made through an interface arrangement between the driver and the autonomous drive system or driver assist system. The interface arrangement may comprise a manually operated communication device such as a touch screen, a button, a switch, a gear stick, a joy stick, or the steering wheel of the vehicle. The communication device may be arranged to be movable between multiple predetermined positions corresponding to pre-defined commands to be input into the autonomous drive system.
However, there may be instances when an automated function is currently unavailable due to external circumstances or circumstances inside the vehicle. Such circumstances may, for instance, be poor weather conditions, poor road conditions, technical failure or technical malfunction.
It is previously known to alert a driver of a vehicle when an assistive/autonomous function in a driver assist system is no longer available.
US20090299573 A1 is directed to an assistive steering system which operates together with driver input to steer and position a vehicle within a lane and adapting the steering of the vehicle to road curvature. It is disclosed that the driver may be required to adjust lateral offset when the vehicle localization is of insufficient quality to precisely pinpoint the vehicle within a lane, while still being sufficient to estimate the curvature of the road.
US20090299573 A1 further discloses that the driver may be aided in monitoring the accuracy of lane prediction by being shown the predicted path of the vehicle as a function of the offset on a display screen. In situations where no lane markers can be identified, and/or on roads not contained in the road database, the system may effectively disable automated steering. As a result, the vehicle direction is not affected by any automated trimming of the steerable tires, and relinquishes any effect on the steering of the vehicle to the driver. If a level of uncertainty about the curvature of the road is too great for safe road/lane-following, the vehicle may disengage the trimming feature and alert its driver, such as by an audible beep or a vibrating steering wheel.
US20120166032 A1 is a further document which is concerned with lane offset control and mentions that if a driver requests lane centering, the system determines if lane centering is available or if it is not available due to circumstances such as ECU (electronic control unit) or communication failures, errors relating to the detection sensors and actuators, or if the lane detection sensors are not able to detect lane markings on the road. If the lane centering system is available the system proceeds to carry out the driver's request.
It has been found that the existing automated systems and assist systems provide a driver with insufficient information in order to aid the driver in deciding when to use the system and when to rely on manual operation.